Multichannel signaling system



Feb. 25, 1941. c E. PIERSON EI'AL I 33 4 uuurzcrmunmn SIGNALING SYSTEM Filed May '14, 1938 8 Sheets-Shegt 2 I48 I J us 5 O.E.PIERSON ATTORNEY v 1941; o. E. PIERSON ETAL 7. MULTICHANNEL SiGNALING SYSTEM Filed May 14, 1958 a sheets sheet s INVENTORS O.E.PIERSON ATTORNEY uunncn'mnm. SIGNALING SYSTEM Filed May 14, 1938 8 Shuts-Shoot 4 INVENTORS O, E. Pl ERSON BY .ADAMS ifiam ATTORNEY 1941- o. E. PIERSON EI'AL 7 MULTICHANNEL SIGNALING SYSTEM Filed May 14, 1958 8 Sheets-Sheet 5 INVENTORS FIG. 5 a 71%? BY 2 (2m ATTORNEY 4 o; E. PIERSON El'AL 3, 47

MULTICHANNEL SIGNALING SYSTEM Filed May 14, 1938 8 Sheets-Sheet 6 96 INVENTORS 3oz o. E. PIERSON }'ro REC. BY DAMS RELAY CHAIN t i (AM ATTORNEY Feb. 25, 1941. o. E. PIERSONETAL MULTICHANNEL SIGNALING SYSTEM Fil'ed May 14, 1938 8 Sheets-Sheet 'T QEPWRSON.

BY fijlM 5 ATTORNEY FIG..7

1941. o. E. PIERSON EI'AL 2,233,347

MULTICHANNEL SIGNALING SYSTEM Filed- May 14, 1938 8 Sheets-Sheet 8 INVENTORS o. E. PIERSON ATTORNEY Patented Feb. 25, 1941 UNITED STATES PATENT OFFICE MULTICHANNEL SIGNALING SYSTEM Application May 14, 1938, Serial No. 207,912

35 Claims.

This invention relates to signaling systems and more particularly to expanding-channel or varioplex telegraph systems wherein a channel or channels of a synchronous multiplex system are shared by a variable number of subchannels or sources of telegraph signals.

The term expanding-channel system as used herein refers to a system in which a variable number of telegraph transmitters or other sending devices are arranged to control receiving devices corresponding to each sending device over a lane of traffic, substantially the entire lane time in the preferred system being divided among the operating transmitters. The lane of traific preferably comprises a plurality of channels of a synchronous multiplex system but may comprise a single channel of such a system, one or more wire or carrier current channels or combinations of different types of communication channels. Hence the expression lane of traflic as used herein designates any suitable route or medium over which signalling is accomplished.

The expanding-channel or Varioplex system thus comprises a multi-channel system in which the number of subchannels operating over the connecting circuit or lane of traffic may be expanded or contracted by cutting in or out transmitting and receiving devices, the operative subchannels sharing the lane of trafiic. The present ,30 invention relates particularly to a printing telegraph system of this character in which message characters are sent in sequence from onebusysubchannel transmitter after another, omitting the idle or inoperative subchannels, although not limited to such systems.

One object of the present invention is to provide an expanding-channel system in which the means for connecting the respective subchannels to the lane of traific for operation comprise a chain or series of connector relays with means for operating the relays in sequence while omitting the relays corresponding to inoperative subchannels.

Another object of the invention is to provide an expanding channel system having connector relays for connecting sub-channels to the lane of traffic, a group of relays for each channel of the lane of traffic comprising a relay individual to each subchannel in each of said groups, and in which the connector relays upon operating prepare a circuit for operating a relay in another of said groups.

Another object of the invention is to provide an expanding channel system having a series of connector relays for connecting subchannels to the lane of traffic with means for operating said relays in sequence to connect operative subchannels one after the other to the lane of traffic and in which the connector relays corresponding to operating subchannels remain op- -5 erated under certain conditions, as for example when the number of operative subchannels does not exceed the number of channels provided by the lane of traffic.

Another object of the invention is to provide an expanding channel system having connector relays for connecting operative subchannels to the lane of traflic, each of said connector relays being provided with separate operating and locking windings, and means for controlling the circuits of one or both of said windings of the respective connector relays in accordance with the transmission of characters over the lane of traffic, as for example by a momentary current impulse from the multiplex distributor wherezo the Lane of traffic comprises a synchronous multiplex system.

Another object of the invention is to provide an improved relay chain for controlling a multiplicity of circuits, more particularly for connecting a plurality of circuits one after the other to another circuit or alternately to a plurality of other circuits.

Another object of the invention is to provide an expanding channel system in which the lane '30 'of triafiic consists of a synchronous multiplex system, and a single distributor-transmitter for each multiplex channel, each distributor-transmitter being common to all of the subchannels Another object of the invention is to provide an expanding channel systemin which the lane of traihc consists of a synchronous multiplex system, said expanding channel system including means for transmitting a predetermined character such as figures shift over a channel or channels of the multiplex system during idle periods.

Another object of the invention is to provide an expanding channel system having improved means for cutting the receiving ends of subchannels in and out and in which transmission is automatically stopped if a switching signal is distorted in transmission or if a partial switching signal is generated as a result of transmission errors.

Another object of the invention is to provvide an expanding channel system having improved means for cutting subchannels in and out in response to ordinary code combinations not required for communication purposes and 5 for deleting such code combinations if they are inadvertently transmitted from the sending keyboard or tape transmitter.

Another object of the present invention is to provide an expanding channel system embodying improved control functions, for example arrangements permitting the operator or attendant at the transmitting station to stop transmission to him from the remote station as well as to stop his own transmission; and an arrangement to instantaneously release all subchannels at the sending and receiving ends to reallocate the subchannels. I

Another object of the invention is to provide an expanding channel system with control channels which are independent of the connectingv means for associating transmission subchannels with the lane of traffic so that failure or lack of synchronism of the connecting means for the communication subchannels will not interfere with the operation of the control channels.

Another object of the invention is to provide an expanding channel system having synchronous control switches at the sending and receiving stations and means including said switches for associating and disassociating subchannels from the system in accordance with the busy or idle condition thereof.

Another object of the invention is to provide an expanding channel system having step-bystep switches at the sending and receiving stations arranged to enter subchannels which have traffic to send and also providing auxiliary control channels, for example, for controlling the operation of the apparatus at one station from the remote station. 7

Another object of the invention is to provide an expanding channel system with auxiliary control means by which transmission may be stopped and started from either the local or the remote station without introducing errors into subsequent transmission.

Another object of the invention is to provide an expanding channel system having automatic means for entering and cutting out subchannels and means for automatically stopping transmission if the subchannel connecting means at the sending and receiving stations falls out of synchronism.

For a better understanding of the present invention reference may be had to the accompanying drawings, the eight figures of which taken together constitute a circuit diagram of a system embodying the invention.

Figs. 1 to 5 inclusive represent the transmitting apparatus at one station and Figs. 6, 7 and 8 represent the receiving apparatus at a remote station. It will be understood that the system is ordinarily arranged for two-way communication by duplication of the receiving and sending apparatus at the first and second stations respectively.

The general operation of the system, omitting reference to detailed circuits, is as follows:

The system as shown comprises five subchannels including subchannel transmitting units SI, S2, S3, S4 and S5, Fig. 1, and corresponding receiving units SII, SI2, SIS, SI4 and SI5, Fig. '7. Each subchannel, for example, comprises at the sending end, a tape transmitter I0 having tapecontrolled contact members II arranged to engage the contacts of marking and spacing bus bars I2 and I3 to set up desired code combinations representing message characters, and a stepping magnet I4 to advance the tape through .plex channels.

the transmitter; tape perforating means such as a tape reperforator I5 adapted to be controlled by signals received over a circuit I6 from a branch or patrons ofiice; means such as the autostop contacts I8 controlled by the tape arm to indicate that the transmitter unit has message signals to transmit; and an autostop relay I9 controlled by the contacts IS. The tape transmitter I0 may be similar to that disclosed in the patent to Benjamin No. 1,298,440 dated March 25, 1919 or any suitable source of signals. The subchannel transmitting unit is intended to represent any source of intelligence signals and may include a keyboard or locally controlled tape transmitter at the transmitting station instead of means for repeating signals from a remote ofiice or substation. Each subchannel at the receiving end comprises a start-stop printer 250 or a printer or reperforator 254.

Allotting circuit means including a plurality of connector relays 20, 2|, 22, 23 and 24 and 39,

3!, 32, 33 and 3 3 are provided to connect the respective subchannels when operative one after the other to the respective channels of the lane of, traffic. As shown, the contacts of the tape transmitter Ill are connected through a cable 26 to five contacts of relays 2i] and 30 in parallel, the corresponding armatures of said relays being connected through cables 21 and 31 respectively to separate channels of the lane of traffic. The other subchannels S2 to S5 are similarly adapted to be connected through the contacts of relays 2i to 24 and 38 to 34 to the same channels of the lane of traffic.

In the system shown the cables 21 and 31 terminate in two storage relay banks comprising relays 49 to M and 45 to 49 respectively. By way of example the lane of-traffic comprises a synchronous multiplex system having a sending distributor SD (Fig.3) at the transmitting station and a synchronous receiving distributor RD (Fig. 6) at the receiving station. The sending distributor SD comprises a rotatable brush arm. 5G provided with brushes engaging the sending rings 5! and 52 and the local rings 53 and 5 5. The first and second channels of the sending distributor SD,

which in the present instance are utilized as the lane of 'traflic of the expanding channel system,

comprise segments I to It of the segmented sending ring 5! and the sending ring 52, connected to the transmitting circuit, line crchannel L extending to the receiving station. As shown the respective segments of the sending ring 5| are connected to the ring hand armatures of the storage relays at to 59 and the associated contacts normally have marking and spacing potential applied thereto whereby the operation of the storage relays underflthe control of the respective operative subchannels serves to set up code combinations on the channls of the multiplex distributor cor-' responding to thecode-combinations set up on the respective tape transmitters Ill.

If only one or two of the subchannels are in operation said subchannel or subchannels are connected through the respective connector relays to one or both of the multiplex channels represented by the ten segments shown on the sending ring 5!, and there is no cyclic operation and release of the connector relays. If however three or more subchannels are in operation the connector'relays 2B2 l and 3[l34 are operated in sequence to send a character from the operative subchannels in order alternately to the two multi- Thus if subchannels SI, S2 and S3 are in operationand the subchannel SI is conlengthening of the tape loop between the nected by the connector relay 20 to the first multiplex channel, while the character set up on the tape transmitter 10 is being transmitted over the multiplex system, connector relay 3| is operated to connect subchannel S2 to the second multiplex channel. Then while the second subchannel is transmitting over the multiplex system, connector relay 22 is operated and the connector relay 20 is released so as to connect subchannel S3 to the first multiplex channel. Then the connector relay 30 is operated to connect the first subchannel to the relay bank associated with the second multiplex channel and so on, each subchannel being connected in sequence to one or the other of the multiplex channels. If the subchannel S4 or S5 had been operative and subchannel S3 inoperative, the connector relays 22 and 32 associated with the third subchannel are passed over in the cycle of operations so that the third subchannel is omitted from the sequence. The connector relays 20 to 24 and 30 to 34 are interconnected as will be described hereinafter so that when any three or more subchannels are operative, the same are connected in sequence to first one and then the other of the multiplex channels.

At the receiving station, Figs. 6, .7 and 8, a similar set of connector relays 230 to 234 and 240 to 244 are provided to connect the two multiplex channels to the receiving devices or printers corresponding to the transmitters 10, one after the other. The receiving distributor RD comprises a rotating brush arm 2M having brushes engaging the receiving rings 2G2 and 203 and the local rings 204 and 205. Segments l to ID of the segmented receiving ring 202 comprising two receiving channels are connected to windings of the receiving relays 2lll2l9 respectively. The receiving relays are polar relays with unbiased armatures and so adjusted that their armatures remain in contact with either their left-hand or right hand contacts when actuated against one or the other contact depending upon the polarity of the signals received over the line L. When marking signals are received over the line circuit, the armatures of the receiving relays are actuated against their left hand contacts, and vice versa; Thus marking or spacing potential is applied through the contacts of the receiving relays to the cam-controlled contacts a, b, c, d, and e of the distributor transmitters 22| and 223 controlled by the release magnets 222 and 224, respectively. The distributor transmitters 22I and 223 may be of the type disclosed in the patent to Rothermel, No. 1,805,374 dated May 12, 1931. The received character code combinations are thus applied through the contacts of the connector relays 230-234 and MEL-244 to the startstop receiving printers 250, 25I, 252 and 253 and the multiplex printer or reperforator 254. As shown,-the distributor transmitters 22I and 223 are further provided with start contacts f'and operating or sixth-pulse contacts y whereby either start-[stop or multiplex receiving units may be controlled directly from the receiving relays 2li|-2 I 9.

The subchannels at the transmitting and receiving stations of the system are automatically cut in when the subchannels have signals to transmit, and out when transmission has been completed from the subchannel. When the transmitting apparatus of a subchannel has signals to transmit this fact is indicated by the closure of the auto-stop contacts [8 upon the perforator l5 and the tape transmitter thereupon a step-.by-step' control switch comprising three switch wipers 60, BI and B2 operated by a stepping magnet 63 starts to hunt for the subchannel to be cut in. At the same time a start signal is transmitted over the multiplex system to initiate the operation of a second stepby-step control switch comprising Wipers 260, 261 and 262 operated by a stepping magnet 263 at the receiving station. Upon each revolution of the distributor brush arms 50 and 20! of the sending and receiving distributors the abovementioned control switches are stepped one contact; When the wipers of the switch at the transmitting station reach the subchannel that should be cut in, another switching signal is transmitted over the multiplex system and the sending and receiving ends of the subchannel are' cutin to take their regular turn with the other operative subchannels. The sending and receiving ends of any subchannel that should be cut out are controlled by the synchronous control switches in a similar manner upon the opening of the auto-stop contacts l8 of the subchannel which has completed transmission.

The switching signal sent to the receiving station is preferably a character signal which does not have to be employed in the transmission of messages. Various character code combinations would besuitable but it is preferred to use a blank or all-spacing code combination, as

this character is not required in ordinary communication and can be used without necessitating any changes in keyboard or printer mechanism. The blank character code combination is used exclusively as a cut-in or cut-out signal and, therefore, means is provided whereby if the all-spacing code combination or blank character is sent from one of the subchannel transmitters this code combination is automatically changed into either a letters shift or figures shift combination depending upon whether the receiving printer is in lower case or upper case. In this manner the blank combinations inadvertently sent from the transmitter are converted into code combinations which are deleted by the printer and which do not effect the entry or cutting-out of a subchannel.

In the preferred embodiment of the invention as shown, an all-spacing code combination is sent over both multiplex channels whenever the receiving end of a subchannel is to be cut in or cut out, one double blank signal to initiate the stepping of the receiving control switch and another to switch the subchannel. The reception of this switching signal efiects the entry of the particular subchannel which has been selected by the wipersZSB, 26l and 262 of the receiving control switch if it has previously been cut out and the cutting out of the subchannel if it has previously been entered. If an all-spacing code combination is received over only one of the multiplex channels which might occur if line trouble or inductive interference mutilated the signals being transmitted, transmission is automatically stopped from all subchannels, the subchannels being disconnected from the system.

When idle periods occur during which one or more multiplex channels are not connected to subchannel-s, means is provided to transmit the figures shift code combination during such idle periods.

The rotary step-by-step control switches at the transmitting and receiving stations comprising the wipers 60, BI and 62 and the wipers 260, 26l and 262 respectively are employed in connection with the multiplex channels to provide auxiliary signalling or control channels. These control channels are independent of the chains of connector relays employed for connecting the subchannels to the multiplex system, and therefore, if loss of synchronism occurs on the relay chains, the control channels are not affected thereby. The key 'iIl, Fig. 4, is connected to contacts of the sending control switch in a manner to stop transmission from the local station and cut out all subchannels when it is operated. The switches II, I2 and 13, Figs. 4 and 5, are likewise connected to contacts of the sendingcontrol switch. The key II when it is operated stops transmission from the remote station over the other half of the varioplex system involving receiving apparatus (not shown) at the station represented by Figs. 1 to 5. The transmission is started from the remote station again by actuating the key I2. The key "I3 when actuated merely serves to operate a signal such as the call lamp 213 at the remote station so that an attendant may be called, or the control circuit at the remote station may be used. for any other desired purpose.

The subchannels may terminate at the receiving static-n on start-stop printers 256-253 or a multiplex printer or reperforato-r 254. The printers may be located at the receiving station or in branch or patrons offices. The reperforator 254 may have an associated tape transmitter by which the corresponding subchannel may be connected through to; another varioplex system or a fully assigned multiplex transmitting channel. By employing the distributor transmitters 22! and 223, the five unit code combinations received over the multiplex system may be converted into seven unit start-stop code. Also, where the receiving channels are connected to multiplex equipment the distributor transmitters are arranged to provide a sixth pulse for the operation of the multiplex units as Will be described. Thus the distributor transmitters are used for transmitting both to receiving devices of the start-stop type and of the multiplex type.

The detailed operation of the system is as follows:

Transmission from operative subchannels Two guard relays TI and I8 (Fig. 4) are provided in connection with the chain of connector relays, relay I! being associated with connector relays 20-424 and relay I8 with connector relays 30-44. -Auxiliary relays 89 to 84 inclusive are provided, one for each subchann'el. These relays are energized as long as the corresponding subchannel has any message characters to transmit. Auxiliary relays 85 to 89 inclusive are also provided in connection with the respective subchannels :and :are operated as long as the corresponding subchamiels are connected for operation. Rectifiers 9!] to 94 inclusive are also provided in the locking circuits of the connector relays, one rectifier being common .to the pair of connector relays associated with each subchannel. These rectifiers are poled to pass current from ground at the rectifier to negative battery.

When the transmission apparatus associated with any of the subchannels is idle and the tape loop is shortened to raise the tape arm of the transmitter I0 and open the associated autostop contacts I8, the auto-control relay I8 and the stepping magnet I4 of the tape transmitter II) are energized through a circuit including the Winding of the stepping magnet I4, the right hand winding of the auto-stop relay I9 and the right hand armature and make contact of said relay. The energization of the stepping magnet I4 withdraws the pins from the tape in the tape transmitter and when the stepping magnet is deenergized the pins are projected through the tape and the transmitter contacts are selectively operated as described in the above mentioned Benjamin patent.

When signals are received over the line circuit :6 the tape loop between the tape reperforator I 5 and the tape transmitter YIB lengthens, thereby permitting theauto-stop contacts I8 to close. Thereupon a circuit is closed from ground through the winding of the stepping magnet I4 of the tape transmitter, the left hand winding of the auto-stop relay I9, the auto-stop contacts I8, the sixth conductor of the cable 26 and the, windings of relay 89 in series relation to positive battery whereupon relay 80 becomes energized. The left hand winding of relay 80 is of low resistance and few turns, whereas the right hand winding thereof is of high resistance and a large number of turns. Therefore the high resistance of the described circuit of relay 80, which may include external resistance as shown, limits the current in this circuit to :a low value, for example,- a few milliamperes. This current is sufficient to energize relay 80 but does not materially afiect the 30 auto-stop relay I9 of :the stepping magnet I 4, and the auto-stop relay and stepping magnet remain energized.

After the subchannels have been connected to the system for operation in a manner to be described hereinafter in response to the energize.- tion of relay til, (or relay 8|, etc.) the tape transm-itter I!) of each operative subchannel is controlled by the stepping mag-net I4 to set up successive character code combinations in accordance with the successive characters perforated on the tape as often as the subchannel is connected to the multiplex transmitting system. The pulsing of the stepping magnets in the respective transmitters is controlled by the local rings of the sending distributer SD through the control relays WI and I02 (Fig. 3) individual to the first and second multiplex channels, respectively. The windings of said relays: are connected in operating circuits which may be traced from positive battery at the local ring 54 through the segment groups 55 and 56 respectively of the local ring 53 of the sending distributer SD, the opposite sides of the windings of said relays being connected to the chain of connector relays in order to effect cyclic operation of the latter in a manner to be described.

The pulsing circuit for the transmitting channel closed in response to the energization of relay Ilil extends from positive battery through the right hand armature and back contact of relay windings thereof are in opposition. The relay I-9 remains deenergizedsin-ce the subsequent step- .ping'pulses traverse both windings of the relay 1 I until transmission has been completed from the subchannel and the auto-stop contacts I8 are opened by the shortening of the tape loop between the transmitter I and reperforator I5. It will be noted that cable 21 is multiplied to the armatures of all the connector relays 20 to 24 whereby the above mentioned stepping pulse for the tape transmitters is directed through the sixth armature of the particular connector relay which energized to the corresponding transmitter.

Similarly a stepping pulse for the second multiplex channel is transmitted through a circuit including the inner armature and front contact of relay I02 and the sixth conduct-or of the cable 31 connected to the connector relays 38 to 34 inclusive associated with the second multiplex channel. In this instance the pulsing circuit includes the sixth armature and front contact of the particular connector relay of the second group associated with the subchannel which is at that moment connected to the second multiplex channel.

When the last message character perforated in the tape at the subchannel transmitter is transmitted from a particular subchannel, for example subchannel SI, the stepping of the tape in the transmitter opens auto-stop contacts I8. The opening of the auto-stop contacts I8 interrupts the above-described stepping circuit through the left hand winding of the auto-stop relay I9 and the current flowing through the right hand winding of said relay when the stepping pulse is received causes the relay to become energized and a locking circuit therefor and for the stepping magnet I4 of the tape transmitter I0 is closed through the righthand armature and make contact of said relay. Upon the energization of the auto-stop relay I9, the above described circuit of relay 80 is interrupted at the make-before-break contacts of the auto-control relay whereupon relay 80 becomes deenergized. This effects the cutting out of the subchannel SI in a manner to be described. Relays 8I to 84, inclusive, are similarly energized when-ever their corresponding subchannels have any trafiic to send and deenergized when the message characters perforated in the tape in each tape transmitter have been sent, and effect the cutting in and out of the other subchannels.

The manner in which the connector relays 20 to 24 and 38 to 34 inclusive, are operated in sequence to connect the'transmitters associated with their respective subchannels to the multiplex channels will be apparent from the following detailed description of the operating circuits. As pointed out above, the control relays 80 to 89, inclusive, are energized when all of the subchannels SI to S5 inclusive are cut in. Assuming that all of the subchannels have been cut in and that connector relays 24 and 33 have previously been operated to connect subchannel S5 to the first multiplex channel and sub-channel S4 to the second multiplex channel, when the brush arm 58 of the sending distributor SD engages the segments 55 of the local ring 53, a circuit is closed from positive battery through the local ring 54, the right hand brushes of the brush arm 50, the segments 55 of the local ring 53, conductor H5, the winding of relay IUI, conductor IIB, the eighth armature and front contact of connector relay 33, the outer left hand armature and front contact of control relay 81, conductor I H, the left hand operating winding of connector relay 22, conductor H8 and the wind ing of guard relay TI to negative battery, whereupon relays I8I and 22 become energized. The energization of relay ,IOI energizes the stepping magnet of the tape transmitter of subchannel S3 as described above. Prior to the energization of relay 22, since connector relay 24 is assumed to be energized as stated above, a circuit is closed from ground through the rectifier 94, the seventh armature and front contact of relay 24, the right hand or locking winding of said relay, conductor I I8 and the Winding of guard relay TI to negative battery, whereby said connector relay 24 has been locked up for the transmission of a character code combination from subchannel S5. Upon the connection of positive battery at the local ring of the sending distributor SD through conductor H8 and the winding of guard relay 11 as described in shunt relation to the locking circuit of connector relay 24, the potential across the locking winding of relay 24 is reversed, thus insuring the rapid deenergization of the relay. Thus relay 24 becomes deenergized the instant that relay 22 is energized. When the local brushes of the sending distributor SD leave the lower segment 55 of the local ring 53 thereby interrupting the operating circuit for connector relay 22, a locking circuit is closed from ground through the rectifier 92, the seventh armature and front contact of relay 22, the right hand locking winding of relay 22, conductor H8 and the winding of guard relay-TI to negative battery, whereby relay 22 remains locked up. The deenergization of relay 24 and the energization of relay 22 substitutes the subchannel S3 for the subchannel S5 in the cyclic operation of the relay chain and the transmitter of subchannel S3 is now connected through the cable 21 to the storage relay bank comprising relays 4D to 44 inclusive associated with the first multiplex channel. The storage relays which receive ground potential from the spacing busbar I3 of the tape transmitter ID of the third subchannel are energized and the right hand armatures of said storage relays connect spacing potential to segments of the first multiplex channel of the sending distributor SD. The front or spacing contacts of the relays 40 to 44 are connected to negative battery through the conductor I25 and the right hand armature and back contact of control relay 96. The back or marking contacts of said control relays are connected to marking or positive battery through the conductor I26 and the left hand armature and back contact of relay I30 (Fig. 5).

Upon the continued rotation of the brush arm 50 of the sending distributor SD, the sending brushes will engage the segments I to 5 of the sending ring 5I whereupon the code combination set up on the storage relays 40 to 44 from the tape transmitter of subchannel S3 are transmitted over the line L. As the local brushes of the brush arm 58 engage the segments 56 of the local ring 53, a circuit is closed from positive battery through the local ring 54, said local brushes and segments 56, the conductor I35, winding of relay I02, conductor I36, the eighth armature and front contact of connector relay 22, conductor I3I, the inner left hand armature and front contact of control relay 86, conductor I47, the left hand operating winding of connector relay 3|, conductor I38, and the winding of guard relay I8 to negative battery, whereupon relays I82 and 3| become energized. Prior to the energization of relay 3!, relay 33 was locked up through a circuit including rectifier 93, conductor I39, the seventh armature and front contact of relay 33, the right hand locking. winding of said relay, conductor I38, and the winding of relay 18 to negative battery. Thus the operation of connector relay 3| by the local brush of the sending distributor SD effects the deenergization of relay 33 at the same time that relay 3| is operated in a manner similar to the operation and deenergization of relays Hand 24 as described above.-

The energization of relay 3! substituted the subchannel S2 for the subchannel S4, the transmitter contacts of subchannel S2 being now connected through the contacts of connector relay 3| and the cable 31 to the windings of the storage relays 45 to 49 associated with the second multiplex channel. The storage relays associated with the second multiplex channel operate in response to spacing potential on the spacing contacts of the tape transmitter of the subchannel and transfer the code combination set up in. said transmitter to the segments 6 toll! inclusive of the sending ring 5! of the sending distributor SD in the same manner as described above, in connection with the first multiplex channel. However the spacing potential on the front contacts of relays 45 to 49 is positive battery which is connected to said contacts through conductor E40 and the right hand armature and back contact of relay 98. The negative marking potential applied to the back contacts of said relays is connected through conductor MI and the left hand armature and back contact of relay [3 I.

As the brush arm of the sending distributor SD'continues to rotate, the connector relays are operated through circuits as described above including contacts of the connector relays which have previously been operated in the following order: relays 20, 34, 23, 32, 2|, 30, etc., whereby the operative subchannels are connected in sequence t-o first one multiplex channel and then the other.

The locking circuits of the connector relays of eachrsubchannel include one of the rectifiers 90 to 94 and those of relays 23 to 24 include'the winding of the guard relay 11, whereas the looking circuits of relays 36 to 34 include the winding of guard relay 78. The operating circuits are similar to those traced above in the foregoing detailed description. Thus the operating circuit of relay 29 includes the conductor I44 and the front contact associated with the outer left hand armature of relay 85. The operating circuit of relay 33 includes the conductor M5 and the front contact associated with the inner left hand armature of relay 95. The operating circuit of relay 2! includes the conductor M6 and the front contact associated with the outer left hand armature of relay 86. Thus the operating circuits for the chain of connector relays include front contacts of the respective control ralays 85 to 89 and it will be apparent that if one of these subchannels is not cut in and the associated control relay is deenergized, the operating circuit for the next relay to be operated is shunted through a back contact of said control relay to the next control relay, thereby passing over the inoperative su bchannel in the cyclic operation of the relay chain. In this manner inoperative subchannels are omitted from the selection, and the transmitting time of the lane of trafiic is divided among the operating channels. Furthermore, if the number of operative subcha-nnels does not exceed the number of multiplex channels, two in this instance, the. operative subchannel or subchannels are permanently connected to the lane of traffic during transmission as the" relay chain does not step.

During the time that one or both of the multiplex channels are idle, the figures shift. code combination is transmitted over the idle channel. If the first multiplex channel is idle, none of the connector relays 20 to- 24 is operated andthe storage relays 40, M, 43 and 44 are all deenergized. Since the guard relay 1'! is deenergized except when. one of the connector relaysZi] to 24 is energized, a. circuit is closed fro-mground through the outer left hand armature and back contact of relay 11, the conductor I50, the third conductor of the cable 2"! and the Winding of fore the storage relays 45, 43, 48 and 49 are'de-" energized Whereas the relay 4'! is energized through a circuit including the left hand outer armature and back contact of relay 18, the conductor wt and the third conductor of cable 31 whereby the figures shift code combination is also set up on the second multiplex channel whenever it is idle.

At the receiving station the code combinations of the transmitted message characters are set up on the segments of the receiving ring 202 of the receiving distributor RD in the usual manner thereby efiecting the corresponding operation of the polar receiving relays 2!!) to 2l9, inclusive. The receiving relay chain is controlled by a group of control relays 28! corresponding to the relays described above in connection with the relay chain at the sending station. It is assumed that the receiving ends of the operating subchannels have been cut in so that the relays 2B5 and 289 corresponding to sending control relays 85 and 85, Fig. 2, of the operative channels have been energized, and that these receiving control relays are arranged to control the receiving relay chain comprising the connector relays 230 to 234 and 248 to 244 in the same manner as the relays at the sending station control the operation of connector relays 20 to 24 and 36 to 34 respectively.

Two relays 3M and 3M corresponding to the transmitter control relays llll and H32 at the sending station are operated from the eighth and ninth segments, and the eighteenth and nine: teenth segments respectively of the local ring 264 of the receiving distributor RD. The release magnets 222 and 224 of the distributor transmitters MI and 223 at the receiving station are energized by the relays 35M and 332 in proper timed relation to the rotation of the brush arm 2M of the receiving distributor to transfer code combinations stored" at the receiving relay bank through the contacts of the receiving connector relays to the receiving devices or printers. As shown, the distributor transmitters 22! and 223 are provided with cam-controlled contacts a, b, c, d and e adapted to close the control circuits of the receiving devices; a start contact f adapted to operate just before the closure of the transmitting contacts a of the distributortransmitter to start the cyclic operation of the start-stop printer 250, 25L 252 or 253; and a sixth-pulse contact 9 connected to the sixth conductor of Cutting subchannels in and out In explaining the operation of connecting and disconnecting the subchannels from the lane of trafilc, it will be assumed that the first subchannel comprising transmitting unit SI and receiving device SII is disconnected from the lane of trafiic but that signals are being received over the line I6 which are to be transmitted to the receiving unit 250 of said subchannel.

As has been pointed out above the control relays 80 and 85 associated with the first subchannel are deenergized when the subchannel is cut out but relay 80 becomes energized as soon as! the transmitting unit has message characters to transmit as indicated by the closing of the auto- I stop contacts IS. The armature of relay 80 is provided with front and back contacts connected respectively to a back contact and a front contact of one of the armatures of relay 85. Thus a test circuit is closed through these contacts whenever either relay is energized and the other relay deenergized which condition occurs when subchannel SI is to be cut in or cut out. manner in which the closure of this test circuit actuates the switching mechanism to cut in or out the transmitting and receiving ends of the corresponding subchannels will now be explained.

It will be noted that each subchannel is provided with a similar test circuit and therefore an explanation of the operation of the switching equipment to enter and cut out any one of the 45 subchannels will be sufficient.

The test circuits of the respective subchannels include the five conductors of a cable I53 which are connected to the armatures of the control relays 80 to 84, inclusive. The conductors in the 50 cable I53 as shown are connected to the first five contacts of the contact bank of the control switch associated with the switch wiper 62. Additional test circuits for additional subchannels may be connected to other contacts of the switch 55 bank such as those represented by the sixth and seventh contacts on the drawing.

When the control relay 80 is energized as described above to close the test circuit of the first subchannel, a circuit is closed from ground 0 through the fifth armature and front contact of relay I54 which is normally energized when the control switch at the sending station is in its initial or rest position as shown through a circuit including the grounded switch wiper 62. The test circuit further includes the first conductor of the cable I53, the armature and front contact of relay 80, the right hand inner armature and back contact of 85, the conductor I55, the conductor I56, left hand inner armature and 70 back contact of relay I51, right hand winding of relay I03, the resistance I58 and conductor I59 connected to the segment 51 of the local ring 53 of the sending distributor SD. When the local brush of the sending distributor engages the segment 51, the described test circuit is closed The thereby energizing relay I03, and thisrelay is locked up through its left hand locking winding, the left hand inner armature and front contact of said relay and the resistance IBI to negative battery. The energization of relay I03 further opens at its right hand armature and back contact the stepping circuit for the subchannel transmitters so that the particular subchannel transmitter which is connected to the lane of traffic for transmission is not operated during this cycle of the relay chain and the character code combination in the transmitter is not sent until said subchannel is later connected in its regular turn to the lane of traffic. It will also be noted that closure of the test circuit of any of the other subchannels causes the energization of relay I03 in a similar manner.

As the local brushes of the sending distributor SD continue to rotate, a circuit is closed from positive battery through the segment 58 of the local ring 53, conductor I64, the left hand outer armature and front contact of relay I03, the right hand winding of relay I30, the conductor I65 and the winding of relay I66 to groundwhereupon relays I30 and I66 become energized. Relay I30 becomes locked up through its left hand winding and left hand inner armature and front contact and the armature and back contact of relay I00. The operation of relay I30, through its left hand outer armature and front contact and the conductor I26, applies negative or spacing battery to the marking contacts of the storage relays 40 to 40 associated with the first multiplex channel so that even though some of these relays may be deenergized an all-spacing or blank character code combination is sent over the line L upon the next revolution of the brush arm of the sending distributor SD.

Upon the energization of relay I66, a circuit is closed from positive battery through the outer armature and front contact of said relay, the inner armature and back contact of relay I10, the conductor I57, the thirteenth armature and front contact of relay I55 and the left hand winding of relay I68 to ground whereupon relay I68 becomes energized. Relay I68 controls the circuit of the stepping magnet 63 of the sending control switch, causing the stepping magnet 63 to be energized and to advance wipers 60, GI and 62 to the first contact position, said relay I68 being provided with a locking winding and looking contacts arranged as shown to insure that the stepping magnet is fully energized even upon a short current impulse applied to the relay I68.

As the sending distributor SD transmits the blank character code combination over the first multiplex channel as described above, a circuit is closed through the local brushes thereof, segment 59 of the local ring 53, conductor III, the

right hand armature and front contact of relay I30, the left hand winding of relay I3I and the resistance I6I to negative battery whereupon relay I3I, becomes energized and relay I03 is deenergized by neutralization of the current through its left hand locking winding. Relay I3I becomes locked up through a circuit including its right hand locking winding, its right hand armature and front contact and resistance I62 to negative battery. The operation of relay I3I through its left hand armature and front contact, applies positive or spacing battery through the conductor MI to the marking contacts of the storage relays 05 to 49, inclusive, associated with the second multiplex channel. Thus even though one or more of the said storage relays may be dedistributor traverse the segments of the second mulitplex channel, a blank or all-spacing code combination is sent over the second multiplex channel also. Thus it will be seen that whenever the relay I133 is energized, a double blank character code combination is sent over the two multiplex channels, this code combination serving to initiate the stepping of the receiving control switch at the same time that the sending control switch commences to step, and, when the wipers of said switches reach the subchannel which is to be cut in or out, to efiect the switching of the .receiving end of the subchannel at the same time that the sending end is cut in or out in a manner which will be described hereinafter.

It will be noted that the deenergization of relay I54 which occurred when the wipers 62 stepped to the first position has removed the ground connection normally applied to the contacts of the sending control switch associated with the test wiper 62 through the front contacts thereof and as the test wiper moves over the associated contacts of the test contact bank, said contacts are grounded one after the other through said test wiper 62. Assuming that the first subchannel is to be out in as indicated by the closure of the test circuit through the front contact of relay 8!) and a back contact of relay and the test circuits of the other subchannels are open, when the local brush of the sending distributor engages the segment 58 of the local ring 53, a circuit is closed from positive battery through the local brushes of the distributor, the conductor I 64, the left hand outer armature and back contact of relay I83, the winding of relay Hill, the twelfth armature and back contact of relay I54 and the left hand winding of relay I558 to ground, whereupon relay Ififi becomes energized to cause the wipers of the sending control switch to step to their second contacts. The energization of relay I60 interrupts at its armature and back contact the locking circuit of relay I30 whereupon this relay becomes deenergized. During the continued rotation of the brushes of the sending distributor SD, a circuit is closed from positive battery through the local brushes, segment 59 of the local ring 53, conductor Ill, and the right hand armature and backcontact of relay I30 to neutralize the current in the locking circuit of the relay I3I whereupon this relay becomes deenergized. The deenergization of relays I83, 430 and I3! as described restores these relays to normal thereby permitting the transmission of character code combinations from operative subchannels while the sending control switch continues to step once during each revolution of the brushes of the sending distributor. However, when the test wiper 62 of the sending control switch engages the fifth contact, a circuit is closed from ground through said wiper and fifth contact, conductor I of the cable I53, and the test circuit through relays 88 and 85 whereupon relay It3 again becomes energized and a double blank character code combination is transmitted over the multiplex channels as de scribed above. The energization of relay I03 also interrupts the above described circuit of relays I68 and I58 so that the sending control switch remains with its wipers in engagement with their fifth contacts for two revolutions of the sending distributor. After the double blank energized as the sending brushes of the sending character code combination has been transmitted as described above relays I93, it and I3I are again deenergized and the sending control switch resumes stepping.

When the second switching signal is transmitted from the sending station at the time when the wipers of the sending control switch were in engagement with their fifth contacts, relay I66 becomes energized in series with re.- lay I30 as described above in connection with the transmission of the first switching signal which started the receiving control switch stepping. Upon the energization of relay H66 as. described a circuit is closed from positive battery through the outer armature and front contact of relay I66, the inner armature and back contact of relay I16, conductor I61, the thirteenth armature and back contact of relay I5 3, the wiper 60 of the control switch in engagement with its fifth contact, conductor I13 and the right hand Winding of relay 85 to ground through conductor III! and the left hand outer armature and back contact of relay I51, whereupon relay 85 becomes energized and locks up through its lefthand locking winding and its right hand outer armature and front contact and resistance I'M to negative battery. The energization of relay 85 opens the test circuit through the con-'- tacts of relay 86, referred to above, and as has been explained enters the transmitting end of the'subchannel SI so that by the energization of the chain relays 20 and 30 this subchannel now shares the transmitting time of the lane of traific with the other operative subchannels.

If the subchannel SI had been previously entered on the lane of traflic and the test circuit is closed by the deenergization of relay 30, the sending control switch operatesto cutout the subchannel and transmit a switching signal to cut out the receiving end of the subchannel at the receiving station. Thesame switching signal is used and upon the reception of this signal if the subchannel is in it is cut out, and if it is out it is entered on the lane of traffic. In cutting out the transmitting end of the subchan n-el, when the wipers of the control switch attire transmitting station reach their fifth contacts in the manner described above, a circuit is closed from ground through the left hand loscking winding of relay 85, the right hand outer arma ture and front contact of said relay, the conductor I15, switch wiper GI which is in engagement with its fifth contact, conductor I16, the

inner armature and back contact of relay I 66,

the winding of slow-release relay I18 and resistance I11 to negative battery whereupon relay I10 becomes energized. Thereafter relays I3 and I66 become energized upon the engagement of the local brushes of the sending dis the associated test circuit has been closed to indicate that the subchannel has completedtransmission.

At the receiving station the reception of the double blank switching signal operates all of the polar receiving relays 2E0 to I29 against their right hand or spacing contacts. The contacts associated with the inner or left hand armaturesof relays 210 to 2, inclusive, are arranged to form two baiile circuits, one of which is closed whenever all of the relays are on their spacing contacts upon reception of a blank or all-spacing code combination and the other circuit is closed for all other code combinations. Thus, it will be seen that when the armatures of all of the relays 2I0 to 2M are actuated against their right hand contacts and the local brush of the receiving distributor engages the segment l5 of the local ring 204, a circuit is closed from positive battery at the local ring 205 through the local brushes of the receiving distributor, the left hand armatures and spacing contacts of relays 2M, 2l3, 2l2, 2| I and 210, respectively, conductor 283, the windings of relays 280 and 266 to ground. If, on the other hand, oneor more of the receiving relays 2!!! to 2| 4 had been actuated to marking position, a circuit is closed from the receiving distributor through the left hand armatures and back contacts of the relays which are operated to spacing position and through the left hand armature and marking contact of the lowest relay operated to the marking position to conductor 284. Similarly the polar receiving relays 2|5 to 2| 9, inclusive, are provided with contacts associated with their left hand armatures forming similar baflie circuits between the fifth segment of the local ring of the receiving distributor and conductors 293 and 294, respectively.

As stated above, a switching signal consists of a double blank character code combination trans- .mitted'over the two channels of the multiplex system. After the first all-spacing code combination has been set up on the receiving segments I to 5 of the receiving ring 202, the local brushes of the receiving distributor close the above described circuit through the fifteenth segment of the local ring 204, the left hand armatures and spacing contacts of relays 210 to, 2M and the conductor 283 for energizing relays 256 and 280. Relay 266 corresponds to relay I66 at the sending station and intiates the stepping of the receiving control switch upon receipt of the first switching code combination. Thus a circuit is closed from positive battery through the left hand armature and front contact of relay 266, the inner armature and back contact of relay 210, the middle armature and front contact of relay 254 and the winding of relay 258 controlling the stepping magnet 263 of the receiving control switch. In this manner the control switch is stepped 01f from the rest position shown and continues to step in synchronism with the sending control switch. As long as character code combinations are received over themultiplex channels, these character code combinations being interspersed with the blank or switching signals as described above, a circuit is closed during each revolution of the brushes of the receiving distributor through the bafiie circuit associated with the first multiplex channel, the conductor 284, the inner armature and back contact of relay 254, and the winding of relay 268. However, when a blank or allspacing code combination is received on the first multiplex channel, as for example upon the en'- gagement of the sending control switch with its fifth contacts associated with the first subchannel as described above, the circuit of relays 289 and 266 is again closed through the bafile circuit of the polar receiving relays of the first channel. 'Ihereupon a circuit is closed from positive battery to the left hand armature and front contact of relay 286, the inner armature and back contact of relay 218, the middle armature and back contact of relay 254, switch wiper 260 of the receiving control switch, which is in engagement with its fifth contact, and the left hand winding of receiving control relay 285 to ground, whereupon the receiving end of the subchannel is cut in by the energization of relay 285 corresponding to relay 85 at the sending end of the subchannel. Relay 285 looks up through its right hand locking winding and the locking circuit shown, said locking winding being then also connected through the switch wiper 26! of the receiving control switch to the winding of relay 210 in a manner similar to the relation of the locking winding of relay 85 to the auxiliary relay I10 at the transmitting station. Thus, if the relay 285 is locked up when the switching signal is received over the channel, the consequent operated position of relay 270 causes the unlocking of said relay 285 thereby cutting out the subchannel in the same manner as at the transmitting end of the system.

In case a blank code combination is received over only one of the multiplex channels it is an indication that the system is not operating properly. Such an occurrence might be the result of inductive interference on the line which distorted the signals being transmitted so that a blank or all-spacing code combination was formed from a'diiferent combination or if the double blank switching signal is being transmitted, one of the blank code combinations being sent over one of the multiplex channels might be distorted into a different code combination. Therefore, if a blank is received over only one channel, the operation of the system is stopped. Thus assuming that the blank is received over the first multiplex channel, as we have seen, this closes the battle circuit through the polar relays m to 254 and energizes relays 280 and 266, re-

lay 23!) being locked from negative battery through its right hand winding as shown. If the character code combination received now over the second multiplex channel is not an all-spacing combination, a circuit is closed from the fifth local segment of the local ring 204 of the receiving distributor through the contacts of one or more of the receiving relays 2| 5 to H9, the conductor 2% and the left hand armature and front contact of relay 289 for stopping transmission by controlling the circuit including relays corresponding to relays IM and I82 at the sending station. The manner in which relays I8I and I82 stop transmission from both stations will become apparent from detailed description of this operation at the sending station in connection with the control keys 10 and II. As has been pointed out these keys are provided to enable the attendant to stop transmission whenever necessary.

.If it is assumed that the blank code combination was received over the second channel and the preceding code combination transmitted over the first channel had not been a blank, relays 266 and 23B are not energized through the baflie circuit of the first channel. Therefore, when the blank-reading baffle circuit of the second channel is closed, a circuit is closed from the fifth segment of the local ring 204 of the receiving distributor through said bafile circuit, the conductor 293 and the left hand armature and back contact of relay 289 for stopping transmission. Thus the baffle or reading circuits of the receiving relays 2 I I) to 2 I9 are arranged to control the receiving control switch when a double blank code combination is received and to stop transmission when a single blank code combination is received over only one of the multiplex channels.

Since the blank or all-spacing code combination is employed for switching purposes, means are provided for preventing the transmission of all-spacing code combinations that may be inadvertently sent from the subchannel transmitters .to the storage relay bank associated with'the multiplex channels. In accordance with the pre ferred embodiment of the invention if this code combination is set up on any one of the transmitters, it is automatically converted into either figures shift (#3 impulse only spacing) if the remote printer is in upper case or letters shift (all marking impulses) when the remote printer is in lower case. Relays I05 to I09 are provided for the respective sub-channels to record whether the last shift character sent from the subchannel was letters shift or figures shift. The operating circuit of relay I55 may be traced from ground through the two windings of the relay in series, conductors I32 and IM, the outer armature and front contact of either connector relay 28 .or 39, depending upon whether subchannel SI is connected to the first or secondmultiplex channel, and the baflle circuits of the storage relays at to 44 or 45 to 49 of the channels. In the case of transmission over the second subchannel when figures shift is transmitted from the subchannel transmitter onlyrelay t! is energized and a circuit is closed from positive battery through the left hand inner armaturev and front contact of ll, the left hand armatures and back contacts of relays 45, 48, 46 and 49, the outer armature and back contact of relay Hi2, the conductor I33, the outer armature and front contact of relay 3!], the conductor I32 and the two windings-of relay I05 to ground, causing the relay I05 to be energized and locked from positive through its armature and front contact and right hand winding.

Subsequently when a letters shift combination is sentfrom subchannel SI, the conductor I32 associated with the relay I05 is grounded through the above described circuit and the armature and back contact of relay 42 or 41 since all of the storage relays are deenergized when the letters hift or all-marking code combination is received. The closure of this circuit neutralizes the locking current of relay I and said relay becomes deenergized. It will be apparent, therefore, that the operated or unoperated condition of rerr ms to IE9 indicates whether a figures shift or letters shift code combination was last transmitted over the respective subchannels.

If a blank or all-spacing code combination is received from one of the subchannels, for example, in the storage relay bank associated with the first multiplex channel, relays. 4! to M, inclusive, are all energized and a circuit is closed from battery through the left hand inner armature and front contact of relay 42, the left hand armatures and front contacts of relays 46, M, 43 and M, the left hand outer armature and front contact of relay t2 and the winding of relay 95, whereupon relay .96 becomes energized. If the'associated relay IE5 is also energized at this moment indicating that the last shift code combination sent from the first subchannel was the figures shift code combinaticn, the operation of relay 95 closes acircuit frombattery through the armature and front contact of relay I05, the left hand winding of said relay, conductor I32, conductor I3 3, the right hand outer armature and front contact of relay 29, conductor I48, the left hand outer armature and back contact of relay Ifll and the left hand armature and front contact of relay 9% for energizing relay'S'I. Relay 97 controls the connection of the third sending segment of the sending ring 5I to the armature of the third storage relay 42 and the energization of relay 97 connects spacing battery to the said segment of the sending ring 5L At the same time the energization of relay 96 transfers the battery on the spacing contacts of relays t0, 4 I 43 and 44 to marking battery so that the figures shift code combination is transmitted over the first multiplex channel. When a blank or all-spacing code combination is received on the storage relay bank associated with the first multiplex channel, if the relay IE5 had on the first multiplex channel. Relays 98 and 99 associated with the second multiplex channel are interconnected with the storage relay bank of said channel in the same manner as relays 9'5 and 97, respectively. Therefore, blank or all-.

spacing code combinations received on the second multiplex channel are similarly converted to either letters-shift or figures shift ,code combination depending upon whether the distant printer is in lower case or uppercase, so that these code combinations are deleted by theprinter.

In accordance with another feature of the invention means are provided for .resynchronizing the relay. chains :of the transmitting and receiving stations when synchronism is lost in case the conditions are such that one of the transmitting subchannels would be sending to the wind? ,It will be evident that loss of chain synchronism might be caused by failure to cut in or out the" receiving end ,of a subchannel when the transmitting end of said subchannel is cut in or out byreason of the failure of the control apparatus. 7

In the ,case of the expanding channel system shown employing two multiplex channels as the lane .of trafiic, it will be apparent that if three or more subchannels are cut in at the transmitting station and a different number of subchannels are connected at the receiving end, the

transmitters and printers will not be connected in the same order to the multiplex channels and the messages received on each printer will be unintelligible. Therefore loss of chain synchronism under these conditions immediately becomes evident.

However, if the system has two or moresubchannels cut in at the sending station and 1 only. one or none is cut'in at the receiving station, the signals transmitted from at least one subchannel are sent to the wind, that is, no

corresponding record appears on any printer. whereas one printer may be receiving intelligi- In this case the loss of chain synble messages. chronism might not "be recognized promptly.

Therefore, in accordance with the invention means is provided for automatically correcting the non-synchronous condition of the system under these conditions.

Only blanks or figures shift code combinations are sent over a multiplex channel when idle, both of these having the third impulse spacing. However when the channels are in use a large proportion of the character code combinations transmitted have the third impulse marking. Therefore, if code combinations corresponding to ordinary message signals are being transmitted over one of the multiplex channels a circuit is closed at frequent intervals from negative battery through the right hand armature and marking contact of receiving relay 2I2 and the conductor 295 to the back contact of the armature of relay 218 or from the corresponding contact of receiving relay 211 through conductor 296 to the back contact of the armature of relay-211. Since the circuits of guard relays 211 and 218 corresponding to the sending guard relays 11 and 18 include the locking windings of one of the connector relays in the groups 230 to 234 and 240 to 244, these receiving guard relays are only deenergized when one of the groups of connector relays is deenergized. Thus, if character code combinations other than the idle signals referred to above are received on the receiving end of one of the multiplex channels to which no subchannel is connected, a circuit is closed through the armature of either relay 211 or 218, the left hand winding of relay 290, conductor 291 and the twelfth segment of the local receiving ring 204 of the receiving distributor to positive battery at the local'ring 205 when the brushes of the brush arm 261 reach said segment. Relay 296 becomes energized and causes all subchannels to be released whereupon the relay chains are synchronized by re-entering the operative subchannels. Relay 296 corresponds to relay I84 at the sending station and its operation will be apparent from the following description of the Operation of relay I84 upon the closure of the start key 12. In this manner the relay chains are automatically synchronized upon the operation of relay 296 whenever signals are received over a multiplex channel which is not connected to the receiving end of a subchannel.

Manual switching and control features The eighth, ninth, tenth and eleventh contacts of the sending and receiving control switches are allotted to signaling and switching channels, the wipers of the respective switches being shown in engagement with their twelfth contacts in the normal or rest position. The control key 13 is associated with the eleventh contact of the sending control switch and the associated signallamp 213 (Fig. 8) at the receiving station is likewise associated with the relay 21I connected to the eleventh contact of the upper bank of the receiving control switch. When the key 13 is momentarily actuated, a circuit is closed through the contacts of said key for energizing relay I85 and said relay is locked upthrough its left hand armature and front contact and resistance 14 to negative battery. The energization of relay I85 further closes through its right hand armature and front contact a test circuit for energizing relay I03 whereupon wipers 66, 6|, 62 of the sending control switch are'stepped from the rest position and a double blank switching signal is transmitted over the line as described above in case a test circuit associated with one of the subchannels is closed. The circuit of relay I63 may be traced from positive battery at the local ring 54' of the sending distributor through the segment '51 of ring 53, the conductor 1'59, resistance I58, right hand winding of relay I03, the right hand armature and front contact of relay I85, and the eleventh armature and front contact of relay I54 to ground. The energization of relay I63 closes the circuit of relay I66 through its left hand outer armature and front contact, the right hand winding of relay I 30 and the conductor I65 as described above. The energization of relay I66 closes a circuit through its outer armature and front contact, the inner armature and back contact of relay I16, conductor I61, and the thirteenth armature and front contact of relay I54 for energizing relay I66 whereupon the sending control switch is stepped from the rest position by the stepping magnet 63. The switch continues to step upon each revolution of the brushes of the sending distributor as de-- scribed above until the wipers 60, 6| and, 62 engage their eleventh contacts. At this point the circuit of relay I63 is reclosed through the wiper 62, the eleventh contact of the associated contact bank, the right hand armature and front contact of relay I85, and the right hand winding of relay I03 to battery at the local ring of the sending distributor whereupon the second double blank switching signal is transmitted over the lane of traiiic.

On the operation of relay I66, which occurs while the wiper 60 is resting on its eleventh stud position in the same manner as described for the case in which a subchannel is entered, a circuit is closed from positive through the outer armature and front contact of relay I66, inner armature and back contact of relay I16, conductor I61, thirteenth armature and back contact of relay I54, wiper 66 and its eleventh stud position, resistance 14 to negative. This neutralizes the locking current in relay I85, thereby causing relay I85 to be released.

The transmission of the first double blank' switching signal as described upon the operation of the key 13. starts the receiving control switch at the receiving station stepping in synchronism with the sending control switch. The reception of the second double blank switching signal, when the Wipers 260, 26I and 262 of the receiving control switch are in engagement with their eleventh contacts, closes the circuit of relays 280 and 266 as described above. The energization of relay 266 closes a circuit from positive battery through the left hand armature and front contact of relay 266, the inner armature and back contact of relay 266, the inner armature and back contact of relay 216, the middle armature and back contact of relay 254, the wiper 260, the eleventh contact of the associated contact bank and the left hand winding of relay 21I to ground. Relay 21I becomes energized, is locked up through a circuit including its armature and front contact, its right hand winding and the key 214, and closes a circuit through its armature and front contact for lighting the call lamp 213. The call lamp 213 may be employed to summon an attendant at the receiving station who extinguishes the lamp by actuating the key 214 or the operation of relay 21I may be employed for any other desired purpose.

The manual switches or control keys 10, H and 12 are associated with the sending control switch in a manner similar to the key 13 and when any of these switches or keys is operated a test circuit is closed similar to that closed by each of the subchannels to initiate the entering or cutting .76

out of the subcha'nnel. Thus the stepping of the sending and receiving control switches is initiated by the closure of any of these test circuits and when the wipers of the sending control switch reach the subchannel or key which has initiated the switching operation, a second switching signal is transmitted to the receiving station to eifect the desired function at that point through the instrumentality of the receiving control switch which at that moment is operated to the same extent as the sending control switch and thus serves to select the receiving end of the subchannel or control channel. However, it should be noted that the control channels are independent of the transmitting subchannels so that the control equipment is not affected by failure or loss of synchronism of the connector relay chains at the sending or receiving stations.

The key 19 associated with the eighth contacts of the sending control switch is adapted to stop transmission from the station at which the key is located to the remote station. When the key 10 is operated relay I63 becomes energized to transmit a switching signal to initiate the stepping of the receiving control switch in a manner described above. The circuit of relay I03 includes the conductor I5?! from the local ring of the sending distributor, the resistance I58, the lefthand inner armature and back contact of relay I51, the conductor I55, the lefthand make contacts of the key 16, the conductor I86 and the eighth armature'and front contact of relay I54 to ground. The operation of relay I66 in response to the energization of relay I03 as described above operates the relay IE8 to initiate the stepping of the sending control switch.

In order to stop transmission from all subchannels it is only necessary to cut outall of the subchannels and prevent them from being cut in again. Relay'l51 performs both of these func tions for the sending ends of the subchannels and relay 298 performs the function of cutting out the subchannels at the receiving end, since the function of preventing subchannels from being cut in again is only necessary at the sending end. The subchannels are all cut out at the same moment by opening the locking circuits of control relays to 89 at the sending station and of relays 285 to 289 at the receiving station. The locking circuits for relays 85 to 89 include conductor I I8 and the lefthand outer armature and back contact of relay I51. Similarly, the locking circuits of relays 285 to 288 include the righthand outer armature and back contact of relay 298.

The release of relays 85 to 89 and 285 to 289 is properly timed so that it does not introduce errors in the transmission of any message characters just before transmission is stopped. Relay I51 further prevents the sending ends of the subchannels from cutting in again by opening at its lefthand inner armature and back contact the test circuit of the several subchannels which includes the conductors I55 and I56 as described above.

After the stop key 10 has been operated as described above, when the wipers 60, GI and B2 of the sending control switch reach their eighth contacts, the circuit of relay I51 is closed from negative through the lefthand winding of relay I51, the eighth contact and its associated wiper 60, the thirteenth armature and back contact of relay I54, the conductor I61, the inner armature and back contact of relay I10 and the outer armature and front contact of relay I66 to positive battery. Relay I 51 becomes energized and locks up through a circuit including the signal lamp I69, the right hand armature and front contact and the right hand winding of relay I51, to ground at the outer armature of relay I56 or alternatively through the conductor I81 and the right hand make contacts of the stop key 10 to ground. The lighting of the lamp I69 indicates to the attendant that transmission has been stopped either manually by the stop-key 10 or automatically in response to the distortion of switching signals as will be explained hereinafter.

At the same time that the stop relay I51 is operated, the wipers I30 and 260 of the sending and receiving control switches being in engagement with their eighth contacts, a circuit is closed through the wiper 260 for energizing relay 298 to cut outall of the receiving ends of the subchannels. Relay 298 becomes locked up through its inner armature and front contact and right hand locking winding togro-und at the outer armature and back contact of relay 254. Thus relay 298 remains locked up until the receiving control switch returns to normal, whereas the relay I51 remains locked up until the sending control switch returns to normal, or if the stop key 18 which is of the locking :type is still operated, until said key is returned to normal.

The operation of the relay I51 opens the test circuits of the respective subchannels at its inner left hand armature'and back co-ntact'as stated above but does not directly release the relay chain. Were this not the case message characters then in process of transmission would b lost or mutilated. When the local brush of the sending distributor SD engages segments 56 of the local ring 53, a circuit is closed from positive battery at the local ring 53, a circuit is closed from positive battery at the local ring 54 through the segments 56, the conductor I 35, the winding of relay I02, conductor I49, the left hand middle armature and front contact of relay I51, a conductor 552 and the left hand inner armature and front contact of relay 18 for unlocking the associated connector relay of the group 30 to- 34. Since the release of the operated connector relay of this group occurs at a time when the normal transfer of subchannels in this group would be made and while transmission is being effected from one of the subchannels to the first multiplex channel, it will be evident that the relay is released in sucha manner as to avoid the loss'or mutilation of the message character being transmitted from the operative subchannel over the second multiplex channel. The release of the connector relay in the group 30 to- 34 also causes the relay 18 to be released. When the local brush of the distributor SD next engages segments 55 a circuit is closed from positive battery at the local ring 54 through the segments 55, the conductor H5, winding of relay I 0|, the conductor N5, the conductor I24, the middle armature and back contact of relay 18 and the left hand inner armature and front contact of relay 11 for unlocking the associated connector relay of the group 20 to 2d. Since the release of the operated connector relay of this group occurs at a time when the normal transfer of subchannels in this group would be made it will likewise be evident that no mutilation or loss of a character occurs as a result of its release. The release of the relay chain at the receiving ends of the subchannels is efiected in a similar manner in response to the energization of relay 298.

1 Transmission may also'be stopped automatical- 

